Semiconductor Device with Solder Bump Formed on High Topography Plated Cu Pads

ABSTRACT

A semiconductor device has a first conductive layer formed over a substrate. A first insulating layer is formed over the substrate and first conductive layer. A second conductive layer is formed over the first conductive layer and first insulating layer. A second insulating layer is formed over the first insulating layer and second conductive layer. The second insulating layer has a sidewall between a surface of the second insulating material and surface of the second conductive layer. A protective layer is formed over the second insulating layer and surface of the second conductive layer. The protective layer follows a contour of the surface and sidewall of the second insulating layer and second conductive layer. A bump is formed over the surface of the second conductive layer and a portion of the protective layer adjacent to the second insulating layer. The protective layer protects the second insulating layer.

CLAIM TO DOMESTIC PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 12/700,114, filed Feb. 4, 2010, which is a division of U.S.patent application Ser. No. 11/689,282, filed Mar. 21, 2007, now, U.S.Pat. No. 7,682,959, which applications are incorporated herein.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device having a solder bump formedon high-topography electroplated copper pads.

BACKGROUND OF THE INVENTION

Semiconductors, or computer chips, are found in virtually everyelectrical product manufactured today. Chips are used not only in verysophisticated industrial and commercial electronic equipment, but alsoin many household and consumer items such as televisions, clotheswashers and dryers, radios, and telephones. As products become smallerbut more functional, there is a need to include more chips in thesmaller products to perform the functionality. The reduction in size ofcellular telephones is one example of how more and more capabilities areincorporated into smaller and smaller electronic products.

Ball Grid Array (hereinafter referred to as BGA) packaging is widelyapplied to package the integrated circuits of chip sets or graphicchips, etc. Conventionally, the BGA packaging has tin balls provided onthe bottom surface of a substrate and arranged in a form of an array.The balls serve as the leads or pins (conductive media) between a chip(or IC) and a circuit board, replacing the conventional lead frames. TheBGA packaging can provide not only more pins but also more space betweenevery two adjacent pins than that of conventional packaging, under thesame size of substrate. In addition, BGA packaging provides superiorheat dissipation and electrical conductivity by providing shorterconducting paths between the chip and the circuit board.

According to the raw material of the substrate, BGA substrates aredivided into three categories: Plastic BGA (PBGA), Metal BGA (MBGA), andTape BGA (TBGA). The PBGA substrate is made of organic materials such ascompounds of BT resin and glass fiber. It is the most popular BGAsubstrate in the packaging industry.

To meet the need for shrinking package sizes and growing lead counts,flip chip and ball grid array (BGA) technologies have becomeincreasingly popular. Flip chip relates to the attachment of anintegrated circuit to a substrate while BGA relates to the attachment ofa substrate to a printed circuit board or the like. Flip chip BGApackages (FCBGA), which combine the two technologies, are relativelysmall and have relatively high lead counts.

One conventional method of creating components of such wafer levelpackage structures is shown in FIG. 1. A plurality of input/output 202are disposed on a semiconductor substrate 201, and are used to transmitinput or output signals. The input/output 202 are usually made of metal,such as gold (Au), aluminum (Al), or copper (Cu). The semiconductorsubstrate 201 and the input/output 202 are both covered by a passivationlayer 203. The passivation layer 203 is usually made of oxide, (such assilicon dioxide (SiO.sub.2)), nitride (such as silicon nitride(Si.sub.3N.sub.4)), or other organic compounds (such as polyimide (PI)).The passivation layer 203 covers the semiconductor structure so as toprotect circuits on the semiconductor structure 201.

A series of metal protection layers 204 a, 204 b, and 205 are used toprotect the passivation layer 203 from damage. An under bump metallurgylayer (UBM layer) 206 is deposited on the protection layer 205. Theunder bump metallurgy layer 206 is usually made of copper (Cu), CuNi,gold (Au), or alloy, and is used as an adhesion layer for the metalsolder bump 207. The metal solder bump 207 is located over the underbump metallurgy layer 206, and are usually made of conductive materialswhich can be used in electroplating technology, such as Sn/Pb alloy,copper (Cu), gold (Au), nickel (Ni), or indium (In).

In the manufacturing process involving high-topography, electroplatedcopper (Cu) pads, passivation material such as passivation layer 203tends to crack. Hence, the prior art use of protection layers 204 a, 204b, and 205 is implemented as a possible solution to protect thepassivation layer 203. In addition, polyimide (PI)/copper (Cu)interfaces typically located at the bottom of a via are attacked duringthe solder bumping process. Such protective measures as found in theprior art, however, are expensive and involve extra manufacturing stepswhich create additional manufacturing time and complexity in themanufacturing process.

SUMMARY OF THE INVENTION

In light of the foregoing, a need exists for a manufacturing methodinvolving solder bumping, where associated passivation material isprotected, yet manufacturing costs, time and complexities are reduced.

In one embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a substrate,forming a first conductive layer over the substrate, forming a firstinsulating layer over the substrate and first conductive layer, formingan opening in the first insulating layer to expose the first conductivelayer, forming a protective layer over the first insulating layerincluding into the opening of the first insulating layer, and forming abump over the first conductive layer and protective layer to isolate thebump from the first insulating layer.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a substrate,forming a first insulating layer over the substrate, forming aprotective layer over the first insulating layer, and forming aninterconnect structure over the protective layer to isolate theinterconnect structure from the first insulating layer.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a substrate,forming an interconnect structure over the substrate, forming aprotective layer over the interconnect structure, and forming a bumpover the protective layer to electrically connect the bump to a firstportion of the interconnect structure and isolate the bump from a secondportion of the interconnect structure.

In another embodiment, the present invention is a semiconductor devicecomprising a substrate and interconnect structure formed over thesubstrate. A protective layer is formed over the interconnect structure.A bump is formed over the protective layer. The bump is electricallyconnected to a first portion of the interconnect structure and isolatedfrom a second portion of the interconnect structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example prior art semiconductor device having aseries of protective metal layers formed over a passivation layer toprotect the passivation layer;

FIG. 2 illustrates an example semiconductor device;

FIG. 3A illustrates an example first step in a manufacturing process;

FIG. 3B illustrates an example second step in a manufacturing process;

FIG. 3C illustrates an example third step in a manufacturing process;

FIG. 3D illustrates an example fourth step in a manufacturing process;and

FIG. 3E illustrates an example fifth step in a manufacturing process.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the Figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings.

A flip-chip semiconductor package with a lead frame is a combination ofthe lead frame serving as a chip carrier and a flip-chip structure inwhich a semiconductor chip is mounted on the lead frame in a flip-chipmanner. Such semiconductor packages include the lead frame having aplurality of leads, or having a plurality of leads and a die pad; atleast one chip, which is mounted and electrically connected to the leadsvia a plurality of solder bumps formed on an active surface of the chip,or which is mounted on the die pad and electrically connected to theleads via a plurality of solder bumps formed on the active surface ofthe chip; and an encapsulation body for encapsulating the lead frame,the chip and the solder bumps. Flip chip packaging technology providesan advantage that the solder bumps are self-aligned and can becompletely bonded to the leads in a single process, which thereby isrelatively more time and labor-effective, unlike a conventional wiringmethod by which a plurality of bonding wires for the electricalconnection between chip and leads need to be formed one by one.

Since the solder bumps are usually made of tin (Sn) 63/lead (Pb) 37alloy, and the lead frame is made of a solderable metal such as copper,during a reflow process for soldering the solder bumps to the leads, thesolder bumps under a particular high temperature melt and collapse toform eutectic, thus resulting in an intermetallic compound between thesolder bumps and the leads, and which is customarily referred to as awetting step.

Semiconductor structures having electroplated copper (Cu) pad structurescan be incorporated into such flip chip semiconductor devices, or can befabricated for other similar devices or to suit a particularapplication.

Electroplated copper (Cu) pad structures can be thicker than aluminumstructures, generally above 5 microns in thickness. In somemanufacturing processes, materials such as polyimide are disposed abovethe copper structures. As a next step in some manufacturing processes,dry film stripping techniques are then used. The dry film strippingprocess can include strong solvents, which tend to crack materials suchas polyimide, particularly at the junction of the copper pad.

A semiconductor device incorporating high-topography electroplatedcopper (Cu) pad structures can be manufactured with a technique asfollows which serves to protect the passivation surface during thesolder bumping process. In addition, the polyimide/copper (Pi/Cu)interface located at the bottom portion of the via is protected fromfluxing chemicals attacking the interface during a solder reflowmanufacturing process.

Turning to FIG. 2, an example semiconductor device 300 havingincorporated high-topography electroplated copper (Cu) pad structures ispresented which can be manufactured using techniques according to thepresent invention. Device 300 includes a substrate 302. An input/output(I/O) pad 304 is disposed over the substrate to promote electricalconnectivity to the substrate.

A first passivation layer 306 is disposed over a portion of the pad 304and the remainder of the substrate 302 as shown. Electroplated copper(Cu) structures such as copper layer 309 are disposed over the firstpassivation layer, along with an adhesion layer 307 and an optionalbarrier layer 308, depending on the thickness of Cu layer 309. Layers307, 308 and 309 can form a Cu runner structure. The Cu runner 307, 308,309 conducts electrical current from the via to the pad 304. A secondpassivation layer 310 is disposed over the layer 309.

In accordance with the present invention, a portion of a sacrifice layer312 is shown on opposing sides of a solder ball 314 which is formed invias of device 300 as shown. The sacrifice layer 312 is used during themanufacturing process to protect the passivation material, such aspolyimide, from damage. At a later stage in the manufacturing process,the sacrifice layer 312 can be removed to re-expose the passivationmaterial. In one embodiment, the sacrifice layer 312 is removed aftereither dry film/flux stripping. In another embodiment, the sacrificelayer 312 is removed after the completion of a solder bumping process,with the solder bumps used as a hard mask. In either case, thepassivation/copper junction at the bottom of each via is protected fromflux solvents attacking the junction during a solder reflow process.

Turning to FIG. 3A, an example first step of manufacturing device 300 isshown according to the present invention. At the depicted stage shown inFIG. 3A, device 300 includes a Cu runner 309 (redistribution layer)which is deposited and patterned on a first passivation layer 306.Again, layer 306 is deposited on a substrate 302 for structural support,and incorporates an I/O pad 304 to provide electrical connectivity. A Curunner structure, which can include an adhesion layer 307, an optionalbarrier layer 308, and a Cu layer 309 is deposited on the firstpassivation layer 306. Again, the barrier layer 308 is optional anddepends upon the thickness of the CU layer 309.

The adhesion layer 307 can be made of titanium (Ti), titanium/tungsten(TiW), tantalum (Ta), chromium (Cr), or a metal with similar properties.The thickness of the adhesion layer 307 can vary between 200 Angstromsto 1500 Angstroms.

Barrier layer 308 can include nickel-vanadium (NiV), chromium-copper(CrCu), tantalum nitride (TaN), or a similar metal or metal alloy. Thethickness of the barrier layer can range from 400 Angstroms to 4000Angstroms.

Turning to FIG. 3B, an example second step of manufacturing device 300is depicted. A second passivation layer 310 is deposited and patternedover a portion of the Cu runner 307, 308, 309 and a portion of the firstpassivation layer 306 as shown. Layer 310 can include polyimide,benzocyclobutene (BCB), lead oxide (PbO), or similar materials.

At the depicted stage shown in FIG. 3C, device 300 consists of thesubstrate layer 302, the I/O pad 304 formed over the substrate, thefirst passivation layer 306 formed over a portion of the pad 304 andsubstrate 302, copper runners having layers 307, 308, and 309 formedover the layer 306, a second passivation layer 310 formed over thestructures 308, and a sacrifice layer 312 which is initially formed overa portion of the copper layers 307, 308, and 309 and second passivationlayer 310.

Sacrifice layer 312 is deposited and patterned to protect thepassivation surface 310 during the solder bumping process. As shown,sacrifice layer 312 covers and protects the passivation layer 310. Thesacrifice layer 312 can include such materials as titanium (Ti),titanium-tungsten (TiW), tantalum (Ta), silicon nitride (Si₃N₄), silicondioxide (SiO₂), a silicide, or similar materials.

As a next step, the sacrifice layer 312 is patterned with lithography.An opening is etched or otherwise formed in a portion of the layer 312to expose a surface of the copper layers 308 and provide electricalconnectivity. A pair of solder bumps 314 are then formed in the vias ofdevice 300 as shown in FIG. 3B. During the solder bumping process, thelayer 312 acts to protect the passivation material 310 from cracking.

A portion of the sacrifice layer 312 which resides outside the contactof the solder balls 314 and the layer 310 is then removed after eitherone of two processes. The portion of the sacrifice layer 312 can beremoved after a dry film/flux stripping process. In addition, theportion of the sacrifice layer 312 can be removed after the completingof an entire solder bumping manufacturing process, using the solderbumps 314 as a hard mask. The sacrifice layer 312 can be removed using adry etching or wet etching manufacturing process.

Following the removal process, the portion of the layer 312 between thesolder balls 314 and the layer 310 remains, partly to provide structuralsupport. The portion of the layer 312 which lays outside of the solderzone is removed. A next step of manufacturing can then be undertaken fora particular application.

The semiconductor manufacturing techniques previously described can becarried out with tools and materials which are known in the art, such asthe use of patterning or etching equipment. Implementation of amanufacturing technique such as the example method described provides aninexpensive, yet effective method of preserving passivation materialduring the solder bumping process. In addition, the polyimide/copper(Pi/Cu) interface located at the bottom of the via is protected fromfluxing chemicals attacking the surfaces during a solder reflowmanufacturing process.

Semiconductor devices 300 serve to continue to advance semiconductortechnology at reduced fabrication cost, while resulting in largeroverall repeatable quality. Devices 300 eliminate the need to fabricatea series of protective metal layers to protect a passivation materialduring the solder bumping process. In addition, the need to form an UBMstructure is alleviated. Both innovations significantly lowermanufacturing cost, time, and complexity.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

1. A method of making a semiconductor device, comprising: providing asubstrate; forming a first conductive layer over the substrate; forminga first insulating layer over the substrate and first conductive layer;forming an opening in the first insulating layer to expose the firstconductive layer; forming a protective layer over the first insulatinglayer including into the opening of the first insulating layer; andforming a bump over the first conductive layer and protective layer toisolate the bump from the first insulating layer.
 2. The method of claim1, further including: forming a second conductive layer over thesubstrate; forming a second insulating layer over the substrate andsecond conductive layer; and forming a third conductive layer over thesecond conductive layer and second insulating layer.
 3. The method ofclaim 2, further including forming a fourth conductive layer over thethird conductive layer, wherein the first conductive layer is formedover the fourth conductive layer.
 4. The method of claim 1, furtherincluding removing a portion of the protective layer outside a footprintof the bump.
 5. The method of claim 1, wherein the protective layerincludes an insulating material or conductive material.
 6. The method ofclaim 1, wherein the protective layer includes a material selected fromthe group consisting of silicon nitride, silicon dioxide, silicide,titanium, titanium-tungsten, and tantalum.
 7. A method of making asemiconductor device, comprising: providing a substrate; forming a firstinsulating layer over the substrate; forming a protective layer over thefirst insulating layer; and forming an interconnect structure over theprotective layer to isolate the interconnect structure from the firstinsulating layer.
 8. The method of claim 7, further including forming afirst conductive layer over the substrate prior to forming the firstinsulating layer.
 9. The method of claim 8, further including forming anopening in the first insulating layer to expose the first conductivelayer, wherein the protective layer is formed over the first insulatinglayer including into the opening.
 10. The method of claim 8, furtherincluding: forming a second conductive layer over the substrate; forminga second insulating layer over the substrate and second conductivelayer; and forming a third conductive layer over the second conductivelayer and second insulating layer.
 11. The method of claim 8, furtherincluding removing a portion of the protective layer to expose the firstconductive layer.
 12. The method of claim 7, wherein the interconnectstructure includes a bump.
 13. The method of claim 7, wherein theprotective layer includes an insulating material or conductive material.14. A method of making a semiconductor device, comprising: providing asubstrate; forming an interconnect structure over the substrate; forminga protective layer over the interconnect structure; and forming a bumpover the protective layer to electrically connect the bump to a firstportion of the interconnect structure and isolate the bump from a secondportion of the interconnect structure.
 15. The method of claim 14,wherein forming the interconnect structure includes: forming a firstconductive layer over the substrate as the first portion of theinterconnect structure; and forming a first insulating layer over thesubstrate and first conductive layer as the second portion of theinterconnect structure.
 16. The method of claim 15, further includingforming an opening in the first insulating layer to expose the firstconductive layer, wherein the protective layer is formed over the firstinsulating layer including into the opening.
 17. The method of claim 15,further including: forming a second conductive layer over the substrate;forming a second insulating layer over the substrate and secondconductive layer; and forming a third conductive layer over the secondconductive layer and second insulating layer.
 18. The method of claim15, further including removing a portion of the protective layer toexpose the first conductive layer.
 19. The method of claim 14, furtherincluding removing the protective layer outside a footprint of the bump.20. The method of claim 14, wherein the protective layer includes aninsulating material or conductive material.
 21. A semiconductor device,comprising: a substrate; an interconnect structure formed over thesubstrate; a protective layer formed over the interconnect structure;and a bump formed over the protective layer, the bump being electricallyconnected to a first portion of the interconnect structure and isolatedfrom a second portion of the interconnect structure.
 22. Thesemiconductor device of claim 21, wherein the interconnect structureincludes: a first conductive layer formed over the substrate as thefirst portion of the interconnect structure; and a first insulatinglayer formed over the substrate and first conductive layer as the secondportion of the interconnect structure.
 23. The semiconductor device ofclaim 22, further including an opening formed in the first insulatinglayer to expose the first conductive layer, wherein the protective layeris formed over the first insulating layer including into the opening.24. The semiconductor device of claim 22, further including: a secondconductive layer formed over the substrate; a second insulating layerformed over the substrate and second conductive layer; and a thirdconductive layer formed over the second conductive layer and secondinsulating layer.
 25. The semiconductor device of claim 21, wherein theprotective layer includes an insulating material or conductive material.